Conventionally, external connection busbars described in Patent Document 1 are known as examples of external connection busbars that are connected to output electrode terminals of an electricity storage element group. Patent Document 1 describes, in a battery module (electricity storage module) M1 that has a configuration in which a pair of output electrode terminals are used as electrode terminals of electricity storage elements at opposite ends of an electricity storage element group, external connection busbars 19B that are connected to the electrode terminals of the electricity storage elements at the opposite ends. In this configuration, the external connection busbars 19B are held by a resin protector 20, together with busbars 19 that connect the electrode terminals of the electricity storage elements.